Detection of Amp C beta lactamases production in Escherichia coli & Klebsiella by an inhibitor based method.

BACKGROUND & OBJECTIVE: Detection of AmpC-mediated resistance in Gram-negative organisms poses a problem due to misleading results in phenotypic tests. There are no recommended guidelines for detection of this resistance mechanism and there is a need to address this issue as much as the detection of extended spectrum beta lactamases (ESBLs) since both may co-exist and mask each other. Though resistance to cefoxitin is used as a screening test, it does not reliably indicate Amp C production. This study was undertaken to detect Amp C beta lactamases in certain Gram-negative bacteria employing an inhibitor base test using boronic acid. METHODS: A total number of 76 consecutive non repetitive clinical isolates of Escherichia coli (n=67) and 9 Klebsiella pneumoniae (n=9) obtained over a period of two months, were screened for amp C production by disc diffusion method using cefoxitin (30 microg) dics and confirmed by inhibitor based test using boronic acid as inhibitor. RESULTS: A total of 36 of 76 isolates (47.3%) screened harboured amp C enzymes, of which a majority 31 (86.1%) co-produced ESBL enzymes. Pure ampC production was seen in 7 (9.2%) of isolates only. INTERPRETATION & CONCLUSION: Most of the amp C producers also produced ESBL enzymes. The inhibitor based test was useful in identifying cefoxitin susceptible amp C producers and could also effectively differenciate ESBL from amp C producing isolates.

AmpC beta-lactamase producing bacterial isolates from Kolkata hospital.

BACKGROUND AND OBJECTIVE: The widespread use of beta-lactam antibiotics has lead to the development of resistance to this group of antibiotics in bacterial pathogens due to beta-lactamase production. Information on such pathogens is not available from eastern region of India. This study was undertaken to determine the AmpC beta-lactamase production in pathogens isolated from hospitalized patients in Kolkata. METHODS: Non-repeat clinical isolates (284) from pus, urine, sputum and other clinical specimens of hospitalized patients were taken. Disk agar diffusion (DAD) and minimum inhibitory concentration (MIC) with different beta-lactam antibiotics, and double disc synergy test (DDST) with clavulanic acid and sulbactam were done. Disk antagonism test (DAT) and three-dimensional extract test (TDET) were conducted for phenotypic confirmation of AmpC and inducible AmpC beta-lactamase production. Nitrocefin spot test and microiodometric assay of beta-lactamase were also performed. RESULTS: Twenty seven isolates were found to be resistant to cefoxitin, a alpha-methoxy-beta-lactam. Of these, 19 were observed to be AmpC beta-lactamase producers and 4 were inducible AmpC beta- lactamase producers by DDST, DAT and TDET. Remaining 4 were non AmpC beta-lactamase producers. Of the 23 AmpC beta-lactamase producers, the distribution of different species was as follows: Escherichia coli 11 (47.8%), Pseudomonas aeruginosa 4 (17.3%) Klebsiella pneumoniae 3 (13%), and Klebsiella aeruginosa 1 (4.3%). INTERPRETATION AND CONCLUSION: Our finding showed 6.7 per cent AmpC beta-lactamase and 1.4 per cent inducible AmpC beta-lactamase producing clinical isolates from Kolkata. AmpC beta-lactamase producing bacterial pathogens may cause a major therapeutic failure if not detected and reported in time.

Comparative effectiveness and safety of cefotetan and cefoxitin as prophylactic agents in patients undergoing abdominal or vaginal hysterectomy.

In a multicenter, randomized clinical trial, 282 women who underwent abdominal or vaginal hysterectomy were given a single preoperative 2 g dose of cefotetan (171 evaluable patients) or three perioperative 2 g doses of cefoxitin (84 evaluable patients) as antibiotic prophylaxis. A successful clinical response occurred in 92 percent of those receiving cefotetan and 90 percent of those receiving cefoxitin who underwent abdominal hysterectomy, and in 94 percent of those receiving cefotetan and 93 percent of those receiving cefoxitin who underwent vaginal hysterectomy. The incidence of vaginal cuff cellulitis was 3.4 percent and 5 percent for cefotetan and cefoxitin patients, respectively, who underwent abdominal hysterectomy, and 4.8 percent and 4.5 percent, respectively, for those who underwent vaginal hysterectomy. The incidence of major wound infection was 3.4 percent and 2.5 percent for cefotetan and cefoxitin, respectively, in the abdominal hysterectomy group. Postoperative changes in oral body temperature, duration of hospitalization, and postoperative grading of surgical wounds were similar. Both drugs were well tolerated. These results suggest that a single dose of cefotetan is equally effective and as safe as multiple-dose cefoxitin for prophylaxis in patients undergoing hysterectomy.

Studies with temocillin in a hamster model of antibiotic-associated colitis.

Hamsters given the new penicillin temocillin, either orally or by injection, did not develop antibiotic-associated colitis, whereas animals given the control antibiotics cefoxitin or clindamycin developed the disease, which is characterized by marked hemorrhagic cecitis and high cecal levels of Clostridium difficile cytotoxin.

Studies with temocillin in the hamster model of antibiotic-associated colitis.

The studies reported here were designed to ascertain whether or not the new beta-lactam antibiotic, temocillin, would produce antibiotic-associated colitis in the hamster. The experiments were controlled with clindamycin and cefoxitin, which are known to induce antibiotic-associated colitis experimentally and clinically. All three antibiotics were administered to groups of animals both parenterally and orally. Clindamycin, at 1 mg/hamster, caused a slow onset of antibiotic-associated colitis by both routes, with death occurring at between 4 and 8 days. 80 to 100% of the animals had diarrhoea and showed signs of haemorrhage and caecal distension, with the caecal contents being Clostridium difficile toxin-positive. The onset of antibiotic-associated colitis after administration of cefoxitin was less marked at the 1 mg parenteral dose, with only 40% of the hamsters showing signs of colitis. At the higher doses of cefoxitin, colitis was more severe and the animals exhibited dramatic weight loss, with death occurring at between 3 and 5 days. The majority of animals had diarrhoea and were C. difficile toxin-positive; 60 to 80% also showed signs of haemorrhage and caecal distension. In contrast, the hamsters receiving temocillin remained healthy with no signs of diarrhoea, and showed consistent weight gain. No pathological abnormalities were observed and the caecal contents were toxin-negative. These results suggest that temocillin therapy in humans is unlikely to cause significant disturbance of the gastrointestinal flora.

Drug immunotoxicological approaches with some selected medical products: cyclophosphamide, methylprednisolone, betamethasone, cefoxitine, minor tranquillizers.

Alterations of the normal immune response were estimated in C57B1/6 mice pretreated with cyclophosphamide, methylprednisolone sodium succinate, betamethasone sodium phosphate or cefoxitine as positive controls and three minor tranquillizers: dipotassium chlorazepate, diazepam and meprobamate. The specific immune response against sheep red blood cells (SRBC) was evaluated by numeration of the direct plaque-forming cells (PFC; humoral immunity) and by measurement of the footpad swelling (delayed-type hypersensitivity, DTH). In our experiments, the results with the positive controls were in the same order as those described by others, and at the dose levels used, these three minor tranquillizers did not really alter the specific humoral and cellular immune response against SRBC in the C57B1/6 mice.

Evaluation of cefoxitin nephrotoxicity in experimentally induced renal failure.

The nephrotoxicity of cefoxitin was studied in a rat model of impaired renal function. Two levels of renal impairment were produced: "moderate," with blood urea concentrations of 100 to 150 mg/100 ml (16.7 to 25.1 mmol/liter) and glomerular filtration rates 25 to 35% of normal, and "severe," with blood urea concentrations greater than 150 mg/100 ml (greater than 25.1 mmol/liter) and glomerular filtration rates 10 to 20% of normal. Sham-operated animals were used as controls. Three dose schedules of cefoxitin were administered to these controls--500, 1,000, and 2,500 mg/kg per day administered as a divided dose for 5 days. Doses given to the moderately and severely uremic animals were adjusted so that serum levels of cefoxitin were similar to those attained in the sham-operated control animals. Concentrations of urea and creatinine in blood, glomerular filtration rates, and the urinary concentrating capacities of the experimental animals were monitored before and after cefoxitin treatment. There was no evidence of nephrotoxicity in even the most challenging experiment, in which blood serum levels of cefoxitin reached 2,000 microgram/ml in animals, with 15% renal function. These findings support available clinical data, suggesting that cefoxitin can be administered safely to patients with compromised renal function.